1. Field of the Invention
The present invention relates to composite printed wiring boards and wireless communication systems, and in particular, to a composite printed wiring board and a wireless communication system that are preferably for use in an RFID (Radio Frequency Identification) system.
2. Description of the Related Art
In recent years, as information management systems for products, RFID systems have been put into practical use in which communication is made, in a non-contact manner utilizing an electromagnetic field, between a reader/writer that generates an induction field and an RFID tag that is added to a product, and specific information is transmitted. The RFID tag includes a wireless IC chip that stores specific information and processes specific wireless signals and an antenna (radiator) that performs transmission and reception of high-frequency signals.
RFID systems may be used for information management of printed wiring boards provided in various electronic apparatuses. For example, an RFID tag that utilizes a ground electrode of a printed wiring board as an antenna is described in PCT International Publication No. WO2009/011144. In the RFID tag, a loop-shaped electrode for achieving impedance matching is provided between a wireless IC chip and a ground electrode. Therefore, an RFID tag that achieves a small signal loss can be implemented with such a simple configuration.
In recent years, due to advanced and multi-functional electronic apparatuses, composite printed wiring boards may be used as printed wiring boards. A composite printed wiring board includes a large-size parent board (main board) and a child board (sub-board) arranged as a specific functional block. The child board is mounted on the parent board. For a composite printed wiring board, by adding an RFID tag to each of the parent board and the child board, information management of the individual boards can be performed. However, a number of RFID tags that correspond to individual boards are required, which results in a complication of a matching circuit and an increase in the size of the individual boards. Furthermore, when the number of RFID tags increases, load, such as signal processing, to be put on the RFID system increases, which results in a complication of the system and an increase in the cost.